Host selection among humans by Anopheles punctulatus was studied in an area of Papua New Guinea endemic for malaria and filariasis. Blood films were made from the stomach contents of freshly engorged mosquitoes found resting on the walls of houses in which the parasite status of the occupants was known. Engorgement rates on humans were non-random but could not be consistently related to the parasite status of individuals in the houses for either malaria or filaria. In some households, anophelines preferentially fed on parasitaemic individuals while in other households aparasitaemic individuals were significantly more often selected. This finding is believed to reflect the fact that malaria and filarial infections in this endemic area are predominantly asymptomatic. There were no significant differences in axillary temperatures between malaria or microfilariae positive or negative individuals.

We investigated the blood-feeding behaviour of a natural population of the human-feeding mosquito Anopheles punctulatus in Iguruwe, Papua New Guinea. In particular we investigated the relationship between the mosquitoes' blood-feeding behaviour and their infection by the malaria parasites Plasmodium falciparum and P. vivax. Female mosquitoes were caught at 4 times of the night, the amount of blood they had obtained was measured and their status of infection was evaluated. Among uninfected mosquitoes the bloodmeal size steadily increased through the night, possibly because they were progressively less likely to be disturbed by human activity as the night drew on. Infected mosquitoes, on the other hand, tended to feed maximally at all times of the night. This suggests that infected mosquitoes were more tenacious in their blood-feeding behaviour, being either less readily disturbed during a bout of feeding (and thus feeding longer) or more likely to return to continue their feed following disturbance (and thus feeding several times). Either change would increase the parasites' rate of transmission. We conclude that in this natural situation the two species of malaria parasites modified the mosquitoes' behaviour with the effect of increasing their own transmission.

Malaria and filaria infection rates were determined for anopheline mosquitoes collected whilst biting and resting in village houses in Papua New Guinea. The number of anophelines infected with both parasites was greater than expected from the infection rates of each parasite and this difference was significant in resting collections. The excess of multiply infected mosquitoes is probably a result of a vector population composed of individuals with differing numbers of opportunities to become infected. Malaria-positive, Anopheles punctulatus from resting catches had a significantly greater number of Stage 3 Wuchereria bancroftilarvae than malaria-negative mosquitoes. However, multiply infected mosquitoes appear to suffer greater mortality than non-infected or singly infected mosquitoes when the filarial worm reaches the third stage. Any potential increase in transmission resulting from multiple infections is thereby offset by a greater mortality rate in these mosquitoes.